Facebook is going beyond the “like” button, CEO Mark Zuckerberg said Tuesday.

The social network is working on something akin to a “dislike” button, Mr. Zuckerberg said during a wide-ranging Q&A at Facebook’s headquarters that was streamed online.

But it won’t be simple. Zuckerberg said Facebook wants to limit use of the button to expressing sympathy when someone posts something sad or upsetting.

Zuckerberg said it was a surprisingly complicated task to build the button. But the company has an idea that it will soon begin testing.

Facebook has been asked about a dislike button for many years, but the company didn’t want to just give users an easy way to criticize a Facebook status. Zuckerberg said Facebook has found that users don’t want to vote down others, but would like to express support when someone shares something sad, such as news about a family member dying or an article about the refugee crisis.

“What they really want is an ability to express empathy," Zuckerberg. “If you’re expressing something sad… it may not feel comfortable to ‘like’ that post, but your friends and people want to be able to express that they understand."

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